Step 1

For the fish stew:In a large, heavy pot over medium heat, warm the oil

Step 2

Stir in the onion, fennel, celery, leeks, garlic, and bay leaf and cook, stirring often, until tender but not browned, 10 to 15 minutes.Stir in the wine and simmer until reduced by half, about 15 minutes.Stir in the stock and water and bring to a boil

Step 3

Add the potatoes and cook until tender, about 10 minutes

Step 4

Strain and reserve the broth and set aside the vegetables

Step 5

Return the broth to the pot and add the fish

Step 6

Simmer until firm, 2 to 3 minutes

Step 7

Divide the fish among the serving bowls.In a small bowl, whisk together 1/2 a cup of the aioli with 1/4 cup of hot broth to temper it

Step 8

Whisk the tempered aioli into the pot of broth

Step 9

Return the reserve vegetables to the broth and rewarm over low heat

Step 10

Season with salt and pepper

Step 11

Ladle over the fish

Step 12

Garnish with parsley and a splash of sherry, If using

Step 13

Serve hot with toast and the remaining aioli.For the Aioli:In a medium bowl, whisk together the garlic, egg yolks, lemon juice, and mustard until smooth

Step 14

Whisking constantly, add in the oil in slow, steady stream, whisking until emulsified

Step 15

Season with salt.